radv,aco: use all attributes in a binding to obtain an alignment for fetch
Instead of assuming scalar alignment for an attribute, we can use the required alignment of other attributes in a binding to expect a higher one.
This uses the alignment of all attributes in the pipeline, not just the ones loaded. This can create slightly better code, but could break pipelines which relied on unused (and unaligned) attributes no being loaded. I don't think such pipelines are allowed by the spec.